Ok I'm new to darkroom work sort of, I have been at it for a year. I have been playing with some lith film and getting some good results, grays and gradients. I have been using Ilford Multi Grade paper developer 1/30, Kodak indicator stop, and Nacco NuFix. The question is I developed two rolls of film the first came out great. The second has a yellow residue on the film. Most of residue will wipe off. Same developer, stop, and fixer. Same times. I tried running it through the fixer again thinking it was weak. No change. What gives???